--- a/rust/hg-core/src/progress.rs	Mon Sep 30 16:02:30 2024 +0200
+++ b/rust/hg-core/src/progress.rs	Mon Sep 30 16:04:51 2024 +0200
@@ -1,5 +1,12 @@
 //! Progress-bar related things
 
+use std::{
+    sync::atomic::{AtomicBool, Ordering},
+    time::Duration,
+};
+
+use indicatif::{ProgressBar, ProgressDrawTarget, ProgressStyle};
+
 /// A generic determinate progress bar trait
 pub trait Progress: Send + Sync + 'static {
     /// Set the current position and optionally the total
@@ -9,3 +16,77 @@
     /// Declare that progress is over and the progress bar should be deleted
     fn complete(self);
 }
+
+const PROGRESS_DELAY: Duration = Duration::from_secs(1);
+
+/// A generic (determinate) progress bar. Stays hidden until [`PROGRESS_DELAY`]
+/// to prevent flickering a progress bar for super fast operations.
+pub struct HgProgressBar {
+    progress: ProgressBar,
+    has_been_shown: AtomicBool,
+}
+
+impl HgProgressBar {
+    // TODO pass config to check progress.disable/assume-tty/delay/etc.
+    /// Return a new progress bar with `topic` as the prefix.
+    /// The progress and total are both set to 0, and it is hidden until the
+    /// next call to `update` given that more than a second has elapsed.
+    pub fn new(topic: &str) -> Self {
+        let template =
+            format!("{} {{wide_bar}} {{pos}}/{{len}} {{eta}} ", topic);
+        let style = ProgressStyle::with_template(&template).unwrap();
+        let progress_bar = ProgressBar::new(0).with_style(style);
+        // Hide the progress bar and only show it if we've elapsed more
+        // than a second
+        progress_bar.set_draw_target(ProgressDrawTarget::hidden());
+        Self {
+            progress: progress_bar,
+            has_been_shown: false.into(),
+        }
+    }
+
+    /// Called whenever the progress changes to determine whether to start
+    /// showing the progress bar
+    fn maybe_show(&self) {
+        if self.progress.is_hidden()
+            && self.progress.elapsed() > PROGRESS_DELAY
+        {
+            // Catch a race condition whereby we check if it's hidden, then
+            // set the draw target from another thread, then do it again from
+            // this thread, which results in multiple progress bar lines being
+            // left drawn.
+            let has_been_shown =
+                self.has_been_shown.fetch_or(true, Ordering::Relaxed);
+            if !has_been_shown {
+                // Here we are certain that we're the only thread that has
+                // set `has_been_shown` and we can change the draw target
+                self.progress.set_draw_target(ProgressDrawTarget::stderr());
+                self.progress.tick();
+            }
+        }
+    }
+}
+
+impl Progress for HgProgressBar {
+    fn update(&self, pos: u64, total: Option<u64>) {
+        self.progress.update(|state| {
+            state.set_pos(pos);
+            if let Some(t) = total {
+                state.set_len(t)
+            }
+        });
+        self.maybe_show();
+    }
+
+    fn increment(&self, step: u64, total: Option<u64>) {
+        self.progress.inc(step);
+        if let Some(t) = total {
+            self.progress.set_length(t)
+        }
+        self.maybe_show();
+    }
+
+    fn complete(self) {
+        self.progress.finish_and_clear();
+    }
+}